Check consistency of the _tools/*md information

[MetalArend]

To check if the information in these files is consistent, we can add some checks:

• Check the required fields are present
• Check if the url's are reachable
• Make sure github, packagist and dockerhub are found
• Check if the page.title and page.url variables are used
• Check the length of the description

This could actually be done in a Jekyll template page, instead of externally, so it can run on the Jekyll container and provide feedback for any level of developer.